To add to what has already been said, a 5 pin relay can be used as a changeover relay or to provide power to two circuits. Don't know what motor we are talking about here or injection system but I do know that on hotwire injection system the main efi relay and fuel pump relay are interchangeable, they both have diodes in them. If you look at the relay it should have a diagram on it showing what it does. The fuel pump and main EFI relays should only be changed for a similar relay rated at 30A with a diode.
The diode is there to protect the components/circuit from back emf. (IIRC)
Now about the terminals, two 87's would be for providing power to 2 separate circuits at the same time when the relay is closed (depends if relay is normally open or normally closed) - that is certainly the case for the main efi relay which sends power to injectors, ECU and air flow meter ( I know that's 3 but there is a splice in there O.K!) Fuel pump relay appears to provide power for fuel pump and lamda sensors. So the 5 pin relays are not changeover in this application ('91 RRC).
Think I've got that the right way round, HTH